1. Field of the Invention
This invention relates to air conditioning systems and heat pump systems and more specifically to an apparatus for operating the compressor.
2. Discussion of the Prior Art
An air conditioning system consists of a motor drive connected to a compressor which pressurizes a refrigerant gas for transfer through suitable piping to a refrigeration coil where the pressurized refrigerant gas is depressurized resulting in cooling. A heat pump includes the same general components but operates in reverse. In the air conditioner, the depressurized gas is returned to the compressor for repressurization. A blower is connected to circulate air about the refrigeration coil so that the cooling effect of the refrigeration coil cools the air from the blower. Ducting is included to direct the air into an area to be cooled. Customarily, the ducting includes a return air flow path to take warm air from this area so that it may be transferred by the blower about the refrigeration coil for cooling and then back to the area to be cooled.
Currently, residential air conditioners include an electric motor connected to the compressor to power the compressor. Customarily, this electric motor is a single phase 230 V 60 Hz alternating current motor that operates at one or two speeds to drive the compressor. In operation, when the thermostat located in the area to be cooled indicates that additional cooling is required, a signal from the thermostat initiates the compressor motor to begin the air conditioning operation. When the cooling has resulted in a lower temperature in the area to be cooled, the thermostat indicates the occurrence of this second cooler temperature by removing the signal from the compressor causing the air conditioner to stop. The starting and stopping of the air conditioner compressor not only results in shorter lifetime for the compressor but results in an inefficient use of electric energy by the motor. The compressors include oil circulation to reduce friction and wear on internal components. However, when the compressor is first started, the oil has not had time to properly circulate resulting in excessive wear during the start-up period effecting the compressor reliability. By increasing the number of speeds of the motor to two speeds, the compressor reliability and energy efficiency are improved somewhat but still compressor starts and stops occur.
It is an object of the present invention to provide an air conditioner/heat pump compressor drive system that drives the compressor at a variable speed in accordance with the cooling or heating requirements.
It is a further object of the present invention to provide the conversion of power from single phase to multiphase at a variable frequency to improve the electric motor performance.